No. IV.] 



631 





REMARKS ON TABLE No. VII. 



observations 



America 



laid 



been used in the construction of the maps. The intermediate parts were 

 by the courses corrected for variation and the estimated distances. The observations 

 for latitude and longitude were made by myself, except those to which a name is 

 affixed. The sun's azimuth, from whence the variations were deduced, were gene- 

 Back or Mr. Hood, whilst I took the corresponding 



rally observed either by Mr. Back 



altitudes with the artificial horizon. The letters B., H., and F., denote by whom the 

 observations were taken. 



The chronometers were either worn in our pockets, or, in the colder weather, sus- 

 pended round our necks, inside of our dresses, and were necessarily much shaken 

 from our mode of travelling ; but, on the whole, they preserved their rates more 

 steadily than might have been expected, especially that of Baird's, No. 1733. We 

 ascertained their rates as often as an opportunity offered, and those assigned to 

 them, on leaving Cumberland-House, Fort Chipewyan, and Fort Enterprise, were 

 fixed by a. series of observations. Previous to the commencement of our journey from, 

 the latter place in particular, care was taken to render them as correct as possible. 

 Several observations of the transit of the sun and the star Arcturus over the meridian, 

 as well as equal altitudes and separate observations of the sun's lower and upper 

 limbs were observed. The longitudes, from whence their errors for mean Greenwich 

 time were deduced at each of the different stations, were procured in the following 

 manner: That of Cumberland-House was ascertained by the mean of the chronometers, 

 shewn by an observation on the day of our arrival. The longitude of Fort Chipe- 

 wyan was determined by several lunar observations on each side of the moon, the mean 

 of those of O E. D being 111° 17 38" W., and of those of o W. J) 111° 20' 12" W. 

 The longitude of Fort Enterprise was obtained in the following manner : The mean 

 of the chronometers gave 113° 2' 37" W., at the time of our arrival in August, 1820 ; 

 but that of 1733, which was found by subsequent observations to have preserved its 

 rate more steadily than the others, was 113° 4' 26" W. The mean of several sets of 

 lunars in this month gave o E. D 113° 3' 56" W., but the corresponding observations 

 O W. ) could not then be obtained. 



In the month of May, 1821, several sets of lunars were observed, on each side of 

 the moon, which gave a result of 113° 8' 12" W. The mean between this longitude, 

 and that shewn by all the chronometers, is 113° 5' 24" W., and between it and the 

 result of 1733 is, 113° 6' 19". Fort Enterprise was therefore placed in 11 3° 6' 00' W. 



